Microchip for Sorting and Identifying Large Numbers of Circulating Tumor Cells

Detection and classification of circulating tumor cells (CTCs) may soon become a common method for screening for multiple types of cancer. Fluorescence-activated cell sorting (FACS) is popular one technique for spotting CTCs, but it’s limited because the number of available dye colors is small and because for CTCs of certain cancers there aren’t any markers at all. Since few markers exist, the signal is often vague because multiple cell types end up being collected into the same container.

At the Fraunhofer Institute for Biomedical Engineering IBMT in Sulzbach, Germany researchers have developed a microchip that works with individual cells, placing each one by one on small holes, examining them, and pushing them onward to make space for other cells. The array has approximately 200,000 holes with a slight negative air pressure to hold the cells from running off, allowing a rather large sample of cells to be analyzed.

The cells are pulled out of a sample and placed so that they can be quickly observed through a microscope. Suspicious cells that resemble target CTCs are sent to a secondary examination using an automated pipette where Raman spectroscopy, which relies on how cells scatter light, is used for a secondary identification. Because typical setups involving glass and polymer substrates affect Raman spectroscopy, the researchers used silicon-nitride as the substrate to avoid unnecessary scattering not caused by the cells themselves.

The researchers also envision the new microchip technology to be applicable for drug testing, sorting proteins, and studying how cells behave when present in different environments.